Laterally emitting optical waveguide and method for introducing micromodifications into an optical waveguide

ABSTRACT

The present invention relates to an optical waveguide, comprising an optical wave-guiding core, a region in the optical waveguide, wherein the micro-modifications are arranged in the region of the optical waveguide, wherein the arrangement of the micro-modifications is ordered, and to a method for producing an optical waveguide according to the invention.

This application is a § 371 U.S. National stage of PCT InternationalPatent Application No. PCT/DE2016/100727, filed Jun. 15, 2016, whichclaims foreign priority benefit of German Patent Application No. DE 102015 008 277.9, filed Jun. 19, 2015, and German Patent Application No.DE 10 2015 119 875.4, filed Nov. 17, 2015, the disclosures of each ofwhich patent applications are incorporated herein by reference.

The invention relates to an optical waveguide and a method forintroducing micro-modifications into an optical waveguide.

Optical waveguides known from the prior art generally consist of anoptical waveguide core (referred to as core below) and an opticalwaveguide cladding (referred to as cladding below). Here, fused silicais a conventionally used production material, but the material is notrestricted thereto. In order to ensure a lossless light guidance withinthe core, the refractive index of the cladding is less than therefractive index of the core. As result, total internal reflection canbe employed at the transition between the core and the cladding suchthat the light is guided in the core of the optical waveguide. Sometimesfurther cladding is coated on the cladding. Conventional opticalwaveguides often additionally moreover have a so-called coating and/or abuffer, which can surround the cladding. These additional layers areusually configured in such a way that they serve, in general, for themechanical stability of the optical waveguide and, in particular, ensurethe destruction-free flexibility of the optical waveguide and themechanical protection of the optical waveguide from external influences.

Usually, the light coupled into the core on one side and the lightguided forward within the core in a virtually lossless manner isdecoupled at the other end of the optical waveguide from the opticalwaveguide. In order to change the light path of the light within thecore, it is known practice to introduce modifications into the materialof the core or into the edge region between core and cladding. As aresult of diffracting and/or scattering and/or refracting the light atthese modifications which are describable as interferences, it ispossible to modify the light path in such a way that this renders itpossible to achieve targeted lateral decoupling of at least portions ofthe light guided in the core of the optical waveguide. If the placedmodifications were introduced over a defined path along the core and/orthe edge region between core and cladding, the lateral decoupling canlikewise take place over this defined path.

The regions processed thus can serve as so-called fibre applicators,which are usually embodied at an end of the optical waveguide or elsetherewithin. It is also known to substantially realize these so-calledfibre applicators by attachments placed thereon from the outside. By wayof example, attachments sealed in a watertight manner, which areattached to the optical waveguide at one end of the optical waveguide,are known. Here, the end of the optical waveguide roughened bymechanical and/or chemical means or a liquid mixed with scatteringparticles and circulating in the attachment embodied in a liquid-tightmanner serves to change the light path for the lateral decoupling of thelight. By way of example, such applicators are known from documents DE41 37 983 C2, DE 42 11 526 A1 or DE 43 16 176 A1.

A further embodiment of such an applied applicator, as is known frome.g. DE 101 29 029 A1, U.S. Pat. No. 4,660,925 or U.S. Pat. No.5,196,005, is an attachment embodied as a hollow body, which is fastenedto one end of the optical waveguide. Here, the hollow body is filled bya carrier matrix, e.g. a silicone gel, into which the particles servingas scattering centres have been introduced. Here, the concentration ofthe scattering particles can be distributed homogeneously or increasesequentially towards the end.

Such attached fibre applicators are usually produced from polymermaterials and are therefore very elastic and mechanically resilient, butthey also have decisive disadvantages which are substantially based onthe two-part embodiment of optical waveguide and attached applicator. Byway of example, the thermal capacity of attached applicators is usuallysubstantially lower than that of the optical waveguides. Likewise, thereis the risk of detachment from the optical waveguide in the case of suchapplicators. Usually, the various manufacturers of such attachedapplicators use different materials, as a result of which differentthermal and mechanical properties of the applicators emerge accordinglyand these are only suitable for specific wavelengths and powers. Thismakes interchanging between various applicators significantly moredifficult, especially since these fibre applicators are optimized forspecific applications. A further decisive disadvantage of attachedapplicators lies in the manufacturing process. Assembly is usuallycarried out manually and it is not automated as a result of thecomplexity thereof. Moreover, there can be a bubble or foreign bodyinclusion during the production, at which light refracts more thanproportionally and this leads to so-called unwanted hotspots, and, as aresult thereof, to a relatively high reject rate.

DE 44 07 547 A1 describes a method for introducing modifications intothe interior of transparent materials using focused laser radiation.Here, micro-cracks which can serve as light scattering centres aregenerated within the transparent material with the aid of laser pulsesin the nanosecond range. Precisely these micro-cracks generated thusconstitute a problem when transferring this method to the application inthe case of optical waveguides. This is because these cracks would leadto such material weakening within an optical waveguide which may have asa consequence the damage or even the breakage of the optical waveguidein the case of thermal or mechanical loading, e.g. when the opticalwaveguide is bent. Moreover, these micro-cracks are not controllable interms of the size and the alignment in relation to the optical waveguideaxis.

DE 197 39 456 A1 has disclosed a method for introducingmicro-modifications acting as scattering centres into an opticalwaveguide. Here, the processing parameters, such as e.g. the pulseduration of the employed laser radiation, are not described in any moredetail and so the exact manifestation of the arising micro-modificationsis undetermined. However, the precise form has a decisive effect on theemission and mechanical stability of the optical waveguide.

Likewise, EP 1342487 B1 has disclosed a laser applicator comprising anoptical waveguide having scattering means suitable for at least partlyscattering the light guided in the interior out of the core of theoptical waveguide, with at least some of the scattering centres forminga diffraction grating.

Although methods suitable for introducing scattering centres into theinterior of the optical waveguide are described, the exact adjustment ofthe parameters required for controlling the manifestation of thescattering centres in a targeted manner is not described.

WO 2004/005982 A2 describes a method for the microstructuring of opticalwaveguides, in which use is made of ultrashort laser pulses. This methodand the method specified above are worded in general terms and containspecifications in respect of the form, size and arrangement/distributionof the generated microstructures without discussing a specific design inview of the thermal and mechanical stability, both in respect of themicrostructures and in respect of the processed optical waveguides.

It is known that a mechanical failure (break of the optical waveguide)may arise during bending or in the case of a different (e.g. mechanicaland/or thermal) load on the optical waveguide if the tensions occurringin the interior of the optical waveguide influence the mechanicalstability too strongly. Micro-cracks may already arise in the outerregion of the optical waveguide cladding during the production process,in particular in the case of a drawing process. The tensions arisingthus can be dissipated by way of the mechanical connection between thecoating (and/or the buffer) and the lateral surface of the cladding suchthat there is no amplification (so-called crack growth) and hence noimpairment of the mechanical stability of the optical waveguide.Furthermore, a known problem is that all in-depth processing of theinterior of the optical waveguide, e.g. of the core or the cladding,impairs the mechanical stability of the optical waveguide. As a result,tensions which can still be tolerated by an unprocessed opticalwaveguide can lead to crack growth in the case of a processed opticalwaveguide, as a result of which the optical waveguide may break.

It is an object of the invention to avoid or reduce one or moredisadvantages of the prior art. In particular, it is an object of theinvention to provide an optical waveguide suitable for radiating atleast some of the light guided in the interior in the lateral directionand, at the same time, comprising a mechanical stability that is as highas possible. Furthermore, it is an object of the invention to provide amethod for introducing micro-modifications into an optical waveguide,said micro-modifications being suitable for radiating at least some ofthe light guided in the interior of the optical waveguide in the lateraldirection.

This object is achieved by an optical waveguide having the features asdescribed and specified hereinbelow and by the features of the methoddescribed and specified hereinbelow for introducing micro-modifications.

The optical waveguide according to the invention comprises an opticalwave-guiding core, a region at the distal end of the optical waveguide,wherein the micro-modifications are arranged in the region in the distalend of the optical waveguide, wherein the arrangement of themicro-modifications is ordered. Compared to an unordered or chaoticdistribution, an ordered distribution of the micro-modifications rendersit possible to control the tension distribution and the emissiongeometry in the optical waveguide. What could happen in the case of anunordered distribution is that further micro-modifications are placedprecisely in the region of tension peaks, said furthermicro-modifications further increasing the tension. This invariablyleads to further mechanical weakening in this region, which may lead todamage of the optical waveguide. If the micro-modifications areintroduced in an ordered manner, the tension distribution can beactively controlled. As a result of this, it is possible for themechanical load to be distributed by the micro-modifications in such away that higher mechanical loads can be introduced during the operationbefore the optical waveguide fails when compared with optical waveguideswith a chaotic distribution of the micro-modifications. Furthermore, theprocessing time can be reduced by a targeted arrangement of themicro-modifications since micro-modifications are only introducedwherever they also expediently contribute to the lateral emission of thelight guided in the optical waveguide. This is not ensured in the caseof an unordered distribution of the micro-modifications. Therefore, moremicro-modifications need to be introduced in the case of an unordereddistribution of the micro-modifications in order to achieve the samelaterally emitted intensity as in the case of an ordered arrangement ofthe micro-modifications.

In a preferred embodiment of the optical waveguide, themicro-modifications are arranged on one or more parallel sectionalplanes, wherein the sectional planes lie perpendicular to the opticalwaveguide axis, and wherein the arrangement of the micro-modificationson the first sectional plane by one or more parameters from a group ofparameters comprising the symmetric arrangement of themicro-modifications, the density of the micro-modifications on the firstsectional plane, the density of the micro-modifications, the size of themicro-modifications, the distance of the micro-modifications from theoptical waveguide axis, the distance between the micro-modifications,the alignment of the micro-modifications or other parameters, with theaid of which the position and distribution of the micro-modifications orthe size or outer form thereof is described.

In a further preferred embodiment of the optical waveguide, thearrangement of the micro-modifications on a first sectional plane isrepeated on at least one other sectional plane. This is advantageous inthat the processing routines can be repeated and a tension distributionproduced by a specific arrangement of micro-modifications can also becontinued over a relatively long region.

In a further particularly preferred embodiment of the optical waveguide,the at least one other sectional plane on which the arrangement of themicro-modifications on the first sectional plane is repeated is rotatedby an angle in relation to the first sectional plane.

In a further particularly preferred embodiment of the optical waveguide,the distance between the first sectional plane and the at least oneother sectional plane on which the arrangement of themicro-modifications is repeated is greater than the extent of a singlemicro-modification.

In a further refinement of the invention, the distance between the firstsectional plane and the at least one other sectional plane on which thearrangement of the micro-modifications is repeated is less than theextent of a micro-modification in the axial direction of the opticalwaveguide for as long as the micro-modifications do not overlap orprevent the beam passage.

In a further particularly preferred embodiment of the optical waveguide,at least one further sectional plane with micro-modifications, which hasa different arrangement to the first sectional plane, lies between thefirst sectional plane and the at least one other sectional plane onwhich the arrangement of the micro-modifications of the first sectionalplane is repeated.

In a further particularly preferred embodiment of the optical waveguide,the micro-modifications on the first sectional plane are arranged in arotationally symmetric manner about the optical waveguide axis.

In a further particularly preferred embodiment of the optical waveguide,the micro-modifications are arranged on a hollow cone, with thelongitudinal axis of the hollow cone lying on the optical waveguideaxis.

In a further particularly preferred embodiment of the optical waveguide,the micro-modifications are arranged on a plurality of hollow cones,with the hollow cones having different diameters and the longitudinalaxes of the hollow cones lying on the optical waveguide axis. Themicro-modifications need not fill out the entire region of the cone upto the tip, as a result of which cut-off cones or spirals on a cone areincluded, among others.

In a further particularly preferred embodiment of the optical waveguide,the region at the distal end of the optical waveguide is subdivided intotwo portions in the direction of the optical waveguide axis, of which afirst portion faces the distal end of the optical waveguide and a secondportion is distant from the distal end of the optical waveguide.

It is likewise a further particularly preferred embodiment to subdividethe processed region of the optical waveguide into at least twoportions, in which different ordered micro-modifications have beenintroduced, in each case in different alignments and embodiments.

The method according to the invention for introducingmicro-modifications into optical waveguides comprises affixing anoptical waveguide in one or more holders, the optical waveguide and/orthe holder being mounted in a movable manner, focusing high-energy laserradiation onto a focal position by way of a focusing apparatus, thefocal position being positionable in the interior of the opticalwaveguide, the radiation being generated by a radiation source withinthe scope of pulsed operation, the focusing apparatus for focusing thehigh-energy radiation being mounted in a movable manner, moving thefocal position through the optical waveguide, wherein the movement ofthe focal position in the interior of the optical waveguide is selectedin a targeted manner dependent on the repetition rate in order togenerate a predetermined arrangement of the micro-modifications.

Preferably, the method for introducing micro-modifications into opticalwaveguides comprises moving the optical waveguide in a rotationalmovement.

In a preferred embodiment of the method for introducingmicro-modifications into optical waveguides, the focal position is movedcontinuously through the optical waveguide.

In a further preferred embodiment of the method for introducingmicro-modifications into optical waveguides moving the focal positionthrough the optical waveguide comprises a combination of rotationalmovements and one or more translational movements.

In a further preferred embodiment of the method for introducingmicro-modifications into optical waveguides, the movement of the focalposition is correlated to the repetition rate in such a way that anordered uniform or systematically changing arrangement ofmicro-modifications arises in the optical waveguide.

In a further particularly preferred embodiment of the method forintroducing micro-modifications into optical waveguides, the arrangementof the micro-modifications is described by one or more parameters from agroup of parameters comprising the symmetric arrangement of themicro-modifications, the density of the micro-modifications on thesectional plane, the size of the micro-modifications, the distance ofthe micro-modifications from the optical waveguide axis, the distancebetween the micro-modifications, the alignment of themicro-modifications or other parameters, with the aid of which theposition and distribution of the micro-modifications or the size orouter form thereof.

In a further particularly preferred embodiment of the method forintroducing micro-modifications into optical waveguides, the incomingbeam direction of the radiation on the optical waveguide is at an anglebetween the optical waveguide axis and the incoming beam direction ofunequal to 90°, in a preferred range at an angle of unequal to 90°+/−5°,in a particularly preferred range at an angle of unequal to 90°+/−10°.

In a further particularly preferred embodiment of the method forintroducing micro-modifications into optical waveguides, the focusingapparatus is additionally made to vibrate in the lateral and transversedirections.

In the method for introducing micro-modifications, use is preferablymade of a laser system which is able to generate ultrashort laserpulses. Here, the pulse length preferably lies in the range between 0.01and 1000 ps, particularly preferably in the range between 0.05 and 10ps, very particularly preferably between 50 and 500 fs. The employedwavelengths reach from the visual to the near infrared range andpreferably lie between 300 and 1500 nm, particularly preferably between500-532 nm or 1000-1064 nm. Here, the range of the employed individualpulse energies preferably lies between 1 μJ and 100 μJ, particularlypreferably between 1 and 50 μJ. From this power densities of between10¹² and 10¹⁵ W/cm² emerge in the focal region.

The used or achievable repetition rate of the laser system decisivelydetermines the processing speed when introducing micro-modificationsinto an optical waveguide. The higher the repetition rate is, the fasterthe focusing apparatus can be displaced in the case of an unchangingdistance between the micro-modifications. Thus, a high repetition rateis preferable as a matter of principle. However, it should be noted herethat the machining axes need to be displaceable in a correspondinglyquick and precise manner. Furthermore, there may be heat accumulationwithin the optical waveguide in the case of very high repetition ratesof greater than or equal to 1 MHz since the energy introduced into theirradiated volume of the optical waveguide can no longer be dissipatedfast enough. This heat accumulation can lead to tension cracks and henceto mechanical instability or even to destruction of the opticalwaveguide. Therefore, a repetition rate is preferably selected in therange from 1 kHz to 1 MHz, particularly preferably between 1 and 100kHz.

The use of ultrashort light pulses (pulse duration ≤10 ps) isadvantageous in that the region of influence of the introduced heatenergy remains very low, as a result of which the introduction ofspatially restricted micro-modifications is made possible withoutdamaging the surrounding material. If laser pulses in the nanosecondrange are used, the energy from an individual pulse is transferred tothe ion lattice of the irradiated material. Like in the case of arepetition rate that is too high, this also leads to heat accumulationin the irradiated material volume and to the formation of microscopictension cracks, the extent of which by all means can lie in themillimetre range. This damage to the material of the optical waveguidecan lead to restrictions in the mechanical stability, right up to apossible break of the optical waveguide under a mechanical and/orthermal load.

The use of ultrashort laser pulses allows a targeted change in thematerial properties only in the irradiated region of a few micrometres,without damaging regions surrounding this in an unwanted manner in theprocess. In this case, the pulse duration does not suffice to transferthe energy to the ion lattice of the surrounding material, and so thereis no, or a strongly reduced, heat accumulation. As a result, it ispossible to generate very small structures with very low tension in thesurrounding material. Both the structures which are small as possibleand the tensions which are as low as possible are necessary conditionsfor the targeted introduction of micro-modifications into opticalwaveguides. Only this allows the targeted structuring of the opticalwaveguide material without ensuring the mechanical stability of theoptical waveguide.

A device comprising a shaft and motor system is provided for the methodfor introducing micro-modifications into optical waveguides. Firstly,this device serves to hold the optical waveguide and, secondly, thedevice allows a targeted displacement and rotation of the opticalwaveguide and it enables arbitrary positioning of the focus of the lasersystem within the optical waveguide. The method according to theinvention and the associated device according to the invention allow anyvariation of the form, the distribution and the position of themicro-modifications within the optical waveguide. As a result of this,it is possible, for example, to influence the position or the form ofthe micro-modifications in a targeted manner by way of the displacementspeed of the linear and rotational axes or by varying the repetitionrate. The distribution of the micro-modifications is also controllablein a targeted manner, for example by way of a so-called laser-internal“pulse picking” or by way of a programmable shutter. The depth of themicro-modifications relative to the surface of the optical waveguidecladding can be influenced by a targeted movement of the focus or by atargeted adjustment of the focusing apparatus. Furthermore, an extensionin depth of the individual micro-modifications can be influenced in atargeted manner by an appropriate selection of individual pulse energy,pulse duration, pulse number (individual pulse, double pulse, multiplepulse), spatial distance and/or time interval, or else by “pulsetailoring”. It is likewise possible to introduce micro-modificationsinto the optical waveguide on the side facing away from the laser systemby way of focusing through the middle of the optical waveguide. Here, itis possible additionally to use lens-like effects of the curved surfaceof the optical waveguide for the focusing in order thus to generatemicro-modifications which have an even shorter extension in depth. Thearrangement of the micro-modifications is also influenced by the focalposition or the positioning of the focusing apparatus relative to theoptical waveguide axis. Thus, the alignment of the micro-modificationcan be controlled by shifting the incoming beam position from the normalof the optical waveguide axis.

Any parameter which can be used to describe the micro-modifications,e.g. the depth position, the spatial extent, the distribution, thedistance from one another, the position, the alignment or else the formof the micro-modifications, can have an influence on the mechanicalstability of the optical waveguide. The smaller the spatial extent ofthe micro-modifications and the greater the distance between themicro-modifications, the smaller the influence is on the mechanicalstability of the optical waveguide. On the other hand, it is also thecase that the strength of the light decoupling caused by themicro-modifications behaves in a substantially opposite manner to theeffects on the mechanical stability. Therefore, it is essential to finda compromise between the decoupled light intensity and the mechanical orthermal stability of the optical waveguide.

Various embodiments are conceivable in relation to the distribution ofthe micro-modifications. By way of example, it is possible to produce adeliberate irregular distribution of the micro-modifications in order toavoid grating effects, such as e.g. interferences, and in order tosimultaneously ensure a uniform distribution of the decoupled light. Onthe other hand, a targeted regular or periodic distribution of themicro-modifications, such as e.g. a Bragg grating or elsemultidimensional photonic structures, is also conceivable. Moreover, theoption exists of placing the micro-modifications so tightly in theinterior of the optical waveguide that these modifications form a linewhich itself has waveguide properties. This line structure can have anylength and the extent thereof relative to the optical waveguide canlikewise have any embodiment; thus, for example, a straight line orspiral or helical embodiment is conceivable.

The described processing options are not restricted to a specific typeof an optical waveguide. By way of a suitable adaptation of theprocessing parameters, it is possible to process any type of opticalwaveguide, such as e.g. hollow fibres, gradient index fibres, novelhigh-tech glass fibres without lead, photonic crystals or photoniccrystal fibres.

Below, the invention will be explained in more detail on the basis of aplurality of example embodiments. In detail:

FIG. 1 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation;

FIG. 2 shows a schematic illustration of an optical waveguide and theinput coupling of focused laser light, and the possibility of relativemovement between the focused laser light and the optical waveguide;

FIG. 3 shows a schematic setup of the processing device for processingoptical waveguides

-   -   a) in a frontal view and    -   b) in a lateral view;

FIG. 4 shows a method for processing optical waveguides using laserradiation;

FIG. 5 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a) showing an optical waveguide and    -   b) showing cross sections along the sectional lines A-A, B-B,        C-C, D-D and E-E;

FIG. 6 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a) showing an optical waveguide and    -   b) showing cross sections along the sectional lines A-A, B-B,        C-C, D-D and E-E;

FIG. 7 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a) showing an optical waveguide and    -   b) showing cross sections along the sectional lines A-A, B-B,        C-C, D-D and E-E;

FIG. 8 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a)-e) showing cross sections along the sectional lines A-A, B-B,        C-C, D-D and E-E and    -   f) showing a cross section along the optical waveguide axis;

FIG. 9 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a)-c) showing various periodic sequences; and

FIG. 10 shows a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation,

-   -   a) showing a sequence of cross sections with different        distributions and/or arrangements of micro-modifications, and    -   b) showing a periodic sequence of regions with the same sequence        of cross sections with different distribution and/or arrangement        of micro-modifications.

FIG. 1 shows a schematic illustration of the optical waveguides (1) tobe machined. The optical waveguide comprises a first region (15) whichis largely free from micro-modifications (5) and a second region (16) ofthe optical waveguide (1) into which micro-modifications (5) have beenintroduced. This region (16) is usually arranged at the distal end ofthe optical waveguide (1). Optionally, the optical waveguide can beprovided with an end cap (14) which prevents light from emerging fromthe end region of the optical waveguide (1). By mirroring the lightwaves, this end cap (14) can guide the latter back to a lateraldecoupling by micro-modifications. The end cap (14) can be replaced bysuitable, direct mirroring of the fibre end surface; this is also inaccordance with the invention. The core (11) is surrounded by cladding(12), followed by a coating and/or a buffer (13). The core (11) andcladding (12) usually consist of quartz and are doped differently. Therefractive index of the cladding material is less than that of the corematerial; in this manner, the light can be transported in the opticalwaveguide (1) as a result of total internal reflection at thecore-cladding transition. The cladding (12) is surrounded by a so-calledcoating and/or buffer (13), which takes up the tension when bending theoptical waveguide (1) and therefore ensures the destruction-freeresilience, and likewise serves for the protection against mechanicaleffects on the layers lying therebelow. For the purposes of processingthe optical waveguide (1), it is possible to remove the buffer (13) thatis not transparent to the selected laser wavelength such that the laserlight only still needs to be focused through the cladding (12). In thecase of the buffer material that is transparent to the selected laserwavelength, e.g. nylon or PTFE, the optical waveguide (1) can also beprocessed through the buffer (13). This is advantageous in that theprocessed region of the optical waveguide (1) substantially has the sameincreased rigidity as the rest of the optical waveguide (1).

FIG. 2 similarly depicts the principle of coupling the focused laserlight (2) into the optical waveguide (1) for introducing themicro-modifications (5). Figure shows the focusing optical unit (21)required for focusing the laser pulses into the core region of theoptical waveguide (1) and the generated micro-modifications (5). In thiscase, important lens parameters for introducing the micro-modifications(5) into the optical waveguide (1) are the focal length and thenumerical aperture (NA) of the symbolically depicted focusing opticalunit (21). The focal length is selected to be as short as possible asthis allows the size of the focal points to be minimized. However, in sodoing, the focal length needs to be long enough to be able to focus intothe core (11) through the optical waveguide cladding. In a preferredvariant, the focal length of the focusing optical unit (21) lies between1 and 5 mm. However, the use of “long-distance” microscope lenses withthe work distance of greater than 5 mm is also a preferred option ofimplementation. An NA of the focusing optical unit (21) which is aslarge as possible is also advantageous since this determines theaperture angle of the focusing optical unit (21). The greater theaperture angle is, the shorter the focal region. This is of greatimportance as it allows the extension in depth of the introducedmodifications (5) to be minimized. The larger aperture angle leads tohigher beam divergence and, as a result thereof, to a quickly increasingbeam diameter upstream and downstream of the focal point. This reducesthe energy density in the regions upstream and downstream of the focusand therefore also reduces the absorption and the risk of damage outsideof the focal region.

In a particularly preferred variant, a short focal length (f<3.1 mm)aspherical lens with a numerical aperture NA>0.68 is used as a focusingoptical unit (21). In a further embodiment, use is made of a speciallens (lens element system) with a high NA. It is constructed in such away that the wavefronts of the focused laser radiation (22) have thesame radius of curvature as the material surface on which they areincident. This is advantageous in that the wavefronts are not distorted(wave front distortion) when passing through the optical waveguidesurface, which in turn leads to a significantly improved focusability inthe material of the optical waveguide (1).

FIG. 3 shows a schematic diagram of the device according to theinvention for introducing micro-modifications into optical waveguides(20). The device (20) comprises various motor-driven adjustment devices(33, 34) for carrying out a linear movement between the opticalwaveguide (1) and the focus of the focused laser beam (22). The movementis preferably carried out in the spatial directions (X, Y, Z) by way oflinear drives (33, 34). Furthermore, the device (20) comprises the setupfor coupling (23) the laser light (2) into the focusing optical unit(24). Furthermore, the device (20) comprises the holder (32) for theoptical waveguide (1) and the axes of rotation (α, β₁, β₂, β₃) forrotation of same. In contrast to the previously known solutions, it isnot the focusing lens that is moved but only the optical waveguide (1).This is advantageous in that there is no need to displace or movedeflection mirrors in the beam path during the processing. As aconsequence, the set up or adjustment outlay for the device issignificantly reduced and, at the same time, an improved long-termstability of the setup emerges since all optical elements can besecurely installed in the beam path. By way of example, in the case ofdeflection mirrors moved by translation, even small inaccuracies ordeviations in the beam path would lead to the laser beam (2) migratingon the focusing optical unit (24). As a result, the focal point migratesboth in the XY-plane and in the Z-direction due to the beam passagethrough the focusing optical unit (24) which is at an angle relative(not perpendicular) to the optical waveguide (1). A setup with long-termstability and reproducible processing results can only be realized withmuch difficulty in this manner or not at all.

The Z-shaft (34) carries the further processing setup consisting of X-and Y-shaft (33), rotation device (31) and holder/guide (32) for theoptical waveguides (1). It serves to move the optical waveguide (1)towards the focusing optical unit (24) or away from the latter. In thismanner, it is possible to vary the distance between the focal point andthe centre point of the optical waveguide (1), i.e. the depth position.The X-shaft (33) serves to displace the optical waveguide or theholder/guide (32) along the extent of the optical waveguide under thefocusing optical unit (24). Thus, the maximum length of a modifiedregion is only determined by the maximum travel of this shaft. TheY-shaft (33) moves the holder/guide (32) at right angles to the extentof the optical waveguide under the focusing optical unit (24). It servesto control the alignment of the micro-modifications (5) since theY-shaft (33) can be used to align the focusing optical unit (24) and theoptical waveguide (1) relative to one another in such a way that thelaser beam (2) is incident as perpendicularly as possible on the opticalwaveguide surface. An oblique incidence on the surface leads to amodified beam path with a distortion of the focal region and thereforeinfluences not only the alignment but also the form and size of theintroduced modifications. The employed laser beam (20) is usually guidedinto the focusing optical unit (24) via a deflection mirror (23),although this is not mandatory. The optical waveguide (1) to beprocessed is held by a holder and guide (32) in an exact position infront of the focusing optical unit (24). This guide is cut out in theregion of the processing or it is transparent to the employed laserradiation (2 and 22). The rotation device (31) serves to rotate theoptical waveguide (1) about the longitudinal axis thereof. To this end,the optical waveguide (1) is fastened to the rotation device (31) bymeans of the tensioning device. In order to avoid excessive torsionaltension of the optical waveguide (1), the latter is in this case alwaysonly rotated step-by-step by up to 360 degrees and subsequently rotatedby up to 360 degrees in the opposite direction. This is realizable bothfor loose optical waveguide portions, e.g. finished optical waveguides,and for roll-to-roll production processes, in which the opticalwaveguides (1) can obtain any length.

FIG. 4 depicts a method for processing optical waveguides (1) usinglaser radiation (2) in one embodiment of the invention. Initially, theoptical waveguide (1) is fixed in terms of its position with the aid ofa holder/guide (32) (41). The holder/guide (32) is designed in such away that the region of the optical waveguide (1) in which themicro-modifications are intended to be generated is accessible for thelaser radiation (2). The optical waveguide is mounted in such a way thatit is movable in three spatial directions in relation to the focalposition. This can be achieved by a movable optical unit (24) and arigid mount of the optical waveguide (1) or by a rigid optical unit (24)and a movably arranged optical waveguide (1). The movement optionscomprise the three spatial directions X, Y and Z and the rotation αabout the longitudinal axis of the optical waveguide (1) and/or therotation β₁, β₂, β₃ about one or more axes. The laser beam (2) isfocused in a further method step (42). The focused laser beam (22) ispositioned in such a way that, with the aid of the movement options, theposition of the focus is movable through the whole region in which themicro-modifications are intended to be introduced. The focal position ismoved by the optical waveguide according to a predetermined pattern(43). Preferably, use is made of a pulsed laser beam. As result of acontinuous movement of the focal position through the optical waveguide(1) with a constant speed, micro-modifications (5) with an equidistantspacing in the movement direction arise. As a result of moving the focalposition through the optical waveguide (1) according to a predeterminedpattern, 20 or more micro-modifications (5) are generated. In apreferred exemplary embodiment of the invention, more than 36micro-modifications (5), particularly preferably more than 360micro-modifications (5) are generated by the movement of the focalposition through the optical waveguide (1) according to a predeterminedpattern. In a further method step, the movement of the focal positionthrough the optical waveguide (1) is repeated according to apredetermined pattern (44).

In a further advantageous refinement, the focal position in relation tothe optical waveguide (1) is modified by a translational and/orrotational movement after completion of the micro-modifications (5)introduced by the movement of the focal position through the opticalwaveguide (1) according to a predetermined pattern. This serves to avoidthat, in the direction of the optical waveguide axis (17), themicro-modifications (5), which were introduced into the opticalwaveguide (1) in the repetition step by the movement of the focalposition through the optical waveguide (1) according to a predeterminedpattern, lie precisely behind the micro-modifications (5), which wereintroduced into the optical waveguide (1) in a first step by themovement of the focal position through the optical waveguide (1)according to a predetermined pattern.

In a further advantageous refinement of the invention, the continuousmovement of the focal position through the optical waveguide (1) iscarried out along the optical waveguide axis and thus subsequentlyresults in one of the described arrangements in the sectional plane.Hence, the processing procedure within a plurality of sectional planesis thus subdivided into the generation of individual points during eachpassage along the optical waveguide axis (17).

In a further advantageous refinement of the invention, the continuousmovement of the focal position through the optical waveguide (1)according to a predetermined pattern is superposed with a furthermovement. By way of example, these movements can be vibrations whichserve to establish a certain lateral offset between themicro-modifications (5), which were introduced into the opticalwaveguide (1) in the repetition step by the movement of the focalposition through the optical waveguide (1) according to a predeterminedpattern, and the micro-modifications (5), which were introduced into theoptical waveguide (1) in the first step by the movement of the focalposition through the optical waveguide (1) according to a predeterminedpattern. Preferably, the amplitude of the vibration is at least half thedistance between adjacent micro-modifications (5). Thus, an orderedarrangement of micro-modifications within the meaning of the presentinvention arises.

The micro-modifications (5) are arranged in the optical waveguide (1) insuch a way that when light passes through the optical waveguide alongthe optical waveguide axis (17), the micro-modifications are arranged insuch a way that the light is deflected to the side as completely aspossible by the micro-modifications.

In a further advantageous embodiment of the invention, themicro-modifications (5) are introduced into the optical waveguide (1) byvirtue of the optical axis (25) of the laser beam (2) being positionedoff the optical waveguide axis (17) on the optical waveguide (1) whenirradiating the optical waveguide (1). In the case ofmicro-modifications (5) whose form deviates significantly from a roundform, i.e. which rather have an elongate form, this renders it possibleto achieve a virtually closed surface or line of micro-modifications (5)by virtue of a rotational movement only.

In a further advantageous embodiment of the invention, themicro-modifications (5) are introduced into the optical waveguide (1) byvirtue of the optical axis (25) of the laser beam (2) being incident onthe optical waveguide (1) at an angle (β₁, β₂, β₃) which is unequal to90° when irradiating the optical waveguide (1). In the case ofmicro-modifications with an elongate form, this results in an acuteangle between the orientation of the micro-modification (5) and theoptical waveguide axis (17). In a further refinement of the invention,the angle (β₁, β₂, β₃) between the orientation of the micro-modification(5) and the optical waveguide axis (17) lies in a range between 10° and80°, in a range between 20° and 70° in a preferred refinement andbetween 30° and 60° in a particularly preferred refinement.

FIG. 5 depicts a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation (partial figure a)) andsectional images along the sectional lines A-A, B-B, C-C, D-D and E-E(partial figure b)). The optical waveguide (1) is configured with a coreregion (11) and a cladding region (12). Micro-modifications (5) wereintroduced into the core region (12) of the optical waveguide (1) by wayof irradiation in accordance with the method (40) according to theinvention. The micro-modifications (5) on the depicted sectional planes(A-A, B-B, C-C, D-D and E-E) are arranged in a rotationally symmetricmanner about the optical waveguide axis (17). On each sectional plane,the micro-modifications (5) have the same distance from the opticalwaveguide axis (17) and they are arranged on a circular arc around theoptical waveguide axis (17). In the sectional plane A-A, themicro-modifications (5) lie close to the cladding (12) of the opticalwaveguide (1) and have a large distance from the optical waveguide axis(17). Over the course of sectional planes B-B to E-E, the distancebetween the micro-modifications (5) and the cladding (12) of the opticalwaveguide (1) increases or the distance between the micro-modifications(5) and the optical waveguide axis (17) decreases. In a furtheradvantageous refinement of the invention, the number ofmicro-modifications (5) arranged on a circular arc in a sectional planedecreases with the distance of the micro-modifications (5) from theoptical waveguide axis (17). This is achieved by virtue of the timeinterval between two laser pulses being modified and/or by virtue of therotational speed being modified.

In a further advantageous refinement of the invention, themicro-modifications are only arranged in one of the sectional planes(e.g. A-A) depicted here, along the entire optical waveguide or in aplurality of circles within one another, i.e. as an arrangement ofsectional planes depicted here that is combined in one sectional plane(e.g. A-A with C-C and/or E-E).

In partial figure a), FIG. 6 shows a schematic setup of an opticalwaveguide with micro-modifications induced by laser radiation. Partialfigure b) depicts the cross sections along the sectional lines A-A, B-B,C-C, D-D and E-E. The optical waveguide (1) is configured with a coreregion (11) and a cladding region (12). By way of irradiation withhigh-energy radiation, micro-modifications (5) were introduced into thecore region (12) of the optical waveguide (1) in accordance with themethod (40) according to the invention. The micro-modifications (5) onthe depicted sectional planes (A-A, B-B, C-C, D-D and E-E) are arrangedin a rotationally symmetric manner about the optical waveguide axis(17). The number and arrangement of the micro-modifications (5) is thesame in each sectional plane. The arrangement of the micro-modifications(5) on the sectional plane B-B is rotated by an angle about the opticalwaveguide axis (17) in relation to the arrangement of themicro-modifications (5) on sectional plane A-A. This rotation of thearrangements of the micro-modifications (5) can be achieved by arotation of the optical waveguide between the processing intervals forintroducing the micro-modifications (5) into the optical waveguide (1).The angle of rotation of the individual sectional planes B-B to E-E inrelation to the sectional plane A-A increases over the course of thesectional planes A-A to E-E. In a further advantageous refinement of theinvention, the number of sectional planes A-A to E-E with differentangles of rotation in a processing interval is selected in such a waythat the arrangement of the micro-modifications (5) of the lastsectional plane of the processing interval E-E would once again lead tothe arrangement of the micro-modifications (5) on the first sectionalplane A-A of the processing interval if the rotation is continued.

FIG. 7 depicts a schematic setup of an optical waveguide withmicro-modifications induced by laser radiation (partial figure a)) andsectional images along the sectional lines A-A, B-B, C-C, D-D and E-E(partial figure b)). The optical waveguide (1) is configured with a coreregion (11) and a cladding region (12). Micro-modifications (5) wereintroduced into the core region (12) of the optical waveguide (1) by wayof irradiation in accordance with the method (40) according to theinvention. The micro-modifications (5) on the individual sectionalplanes (A-A, B-B, C-C, D-D and E-E) are arranged in a rotationallysymmetric manner about the optical waveguide axis (17). On theindividual sectional planes A-A to E-E, the micro-modifications (5) arearranged on a circular arc about the optical waveguide axis (17). Theradii of the circular arcs change over the course of the sectionalplanes A-A to E-E. Furthermore, the arrangement of themicro-modifications (5) on a sectional plane B-B is twisted by an angleabout the optical waveguide axis (17) in relation to the arrangement ofthe micro-modifications (5) on an adjacent sectional plane A-A. Acombination of a rotation about the optical waveguide axis (17) and atranslation of the focused laser beam (22) in relation to the opticalwaveguide (1) is possible between the processing steps for arranging themicro-modifications (5) on the adjacent sectional planes in order toconvert the processing steps for arranging the micro-modifications (5)in a sectional plane A-A into the processing steps for arranging themicro-modifications (5) on an adjacent sectional plane B-B.

In a further advantageous refinement of the invention, themicro-modifications are arranged in only one of the sectional planes(e.g. A-A) depicted here, along the entire optical waveguide, butrotated about the optical waveguide axis, or in a combination ofsectional planes, i.e. as an arrangement of sectional planes depictedhere that is combined in one sectional plane (e.g. A-A with C-C and/orE-E). In a further advantageous refinement of the invention themicro-modifications are arranged in a combination of sectional planes,i.e. as an arrangement of sectional planes depicted here that iscombined in one sectional plane (e.g. A-A with C-C and/or E-E), butwhich changes with every further sectional plane according to thedescribed pattern of the individual sectional planes.

On the basis of cross-sectional images with sections perpendicular tothe optical waveguide axis (17) (partial figures a) to e)) and alongitudinal section along the optical waveguide axis (17) (partialfigure f)), FIG. 8 in each case shows different embodiments of theinvention, which depict different refinements of micro-modifications (5)induced in an optical waveguide by laser radiation. The partial figuresa) and b) show micro-modifications (51, 52) with different sizes. Theposition of the micro-modifications can be selected independentlythereof. The size of the micro-modifications (51, 52) can be influencedby the size of the focus and/or by the amount of energy introduced. Theenergy for an individual pulse can be between 1 and 50 μJ and themicro-modifications become larger with increasing energy, although thisis dependent on the material of the optical waveguide and the laser beamquality. Furthermore, there is the option of arrangingmicro-modifications (5) in such a way that the boundaries thereofcontact or overlap. The form of the micro-modifications (52, 53) canalso be influenced by the form and positioning of the focus.Micro-modifications (53) which have an ellipsoid cross section with alarge ratio of length to width arise in the case of a very elongatefocus, while micro-modifications (52) which have a small ratio of lengthto width arise in the case of a short focal length. The form of themicro-modifications (53, 54, 55, 56) introduces a further parameterwhich can be used for the production of an ordered arrangement of themicro-modifications (5). Partial figures c) to f) depict differentorientations of the longitudinal direction of the micro-modifications(53, 54, 55, 56). The micro-modifications (53) are all oriented in thesame direction in partial figure c). This is obtained if a lateraltranslation in the Y-direction is carried out between optical waveguide(1) and focal position between the pulses of the laser radiation and therefraction arising as a result of the focused laser beam (22) beingincident obliquely on the surface of the optical waveguide (1) iscompensated for by a suitable rotation of the focused laser beam (22)about β₁, β₂ □□□□□□□□ β₃. In partial figure b), the orientations of themicro-modifications (54) are arranged in a rotationally symmetric mannerabout the optical waveguide axis (17) of the optical waveguide (1).During machining, this is achieved by virtue of the optical waveguide(1) rotating about the optical waveguide axis (17) between the laserpulses. The micro-modifications (54) are oriented in such a way that theaxis along the longitudinal direction of the micro-modification (54)through the centre of the micro-modification (54) intersects the opticalwaveguide axis (17) of the optical waveguide (1). Partial figure e)shows the arrangement and orientation of the micro-modifications (5) if,in addition to the processing method for partial figure d), the focusedlaser radiation (22) is not introduced in the direction of the opticalwaveguide axis (17), but the optical waveguide (1) is shifted laterallyin relation to the optical waveguide axis (17). The micro-modifications(55) are then oriented in such a way that an axis along the longitudinaldirection of the micro-modification (55) does not intersect the opticalwaveguide axis (17) of the optical waveguide (1). Partial image f) showsmicro-modifications (56), the axis of which along the longitudinaldirection of the micro-modification (56) through the centre of themicro-modification (56) forms an acute angle (γwith the opticalwaveguide axis (17). The angle (γ) between the orientation of themicro-modification (5) and the optical waveguide axis (17) lies in arange between 10° and 80°, in a range between 20° and 70° in a preferredrefinement and between 30° and 60° in a particularly preferredembodiment. The angle (γ) can be aligned with the tip towards the distalor proximal end of the optical waveguide (1). The arrangement of themicro-modifications can be designed in a rotationally symmetric mannerin relation to the optical waveguide axis (17) and can become narrowertowards the distal and proximal end of the optical waveguide (1).

A movement pattern for arranging and/or orienting micro-modifications(5, 51, 52, 53, 54, 55, 56) in an optical waveguide (1) includes one ormore movements from the group comprising a translation along the spatialdirections X, Y and/or Z and/or rotations about the optical waveguideaxis (17) and/or an axis perpendicular to the optical waveguide axis(17). At least one micro-modification (5, 51, 52, 53, 54, 55, 56) isgenerated in the core (11) of the optical waveguide (1) within amovement pattern. There are one or more movements from the groupcomprising a translation along the spatial directions X, Y and/or Zand/or rotations about the optical waveguide axis (17) and/or a spatialaxis between the movement pattern being carried out a first time and themovement pattern being repeated a second and/or subsequent time. In theprocess, the region in which micro-modifications (5, 51, 52, 53, 54, 55,56) were introduced into the optical waveguide (1) in a first movementpattern and the region in which micro-modifications (5, 51, 52, 53, 54,55, 56) were introduced into the optical waveguide (1) in a secondmovement pattern can overlap.

In partial figures a) to c), FIG. 9 shows the schematic setup of anoptical waveguide (1) with micro-modifications (5) induced by laserradiation. The indicated lines of intersection A, B and C denote regionsin which micro-modifications (5) were introduced into the opticalwaveguide (1) as a consequence of a movement pattern of the focalposition of the focused laser beam (22) through the optical waveguide(1). Partial figure a) depicts a sequence of three different regions (A,B, C) of arrangements of micro-modifications (5) in an exemplary manner,said arrangements repeating once more over the length of the opticalwaveguide. There can also be a multiple number of repeats. The regions(A, B, C) have different arrangements of the micro-modifications. Here,a region (A, B, C) is defined by one or more of the characteristics fromthe group comprising the size, number, orientation, form and/orarrangement of the micro-modifications (5, 51, 52, 53, 54, 55, 56). Themicro-modifications (5, 51, 52, 53, 54, 55, 56) of each region (A, B, C)are induced by a movement pattern of the focal position of the focusedlaser radiation (22) through the optical waveguide (1) and theirradiation connected therewith. As a consequence of the differentarrangements of the micro-modifications (5, 51, 52, 53, 54, 55, 56), thearrangements of the micro-modifications (5, 51, 52, 53, 54, 55, 56) inthe regions (A, B, C) are created by different movement patterns.Between the first instance of carrying out a movement pattern forproducing a region (A, B, C), there are one or more movements of thefocal position in relation to the optical waveguide (1) from a groupcomprising the three spatial directions X, Y and Z and the rotation αabout the longitudinal axis of the optical waveguide (1) and therotation β₁, β₂, β₃ about one or more axes.

Partial figure b) of FIG. 9 depicts a further sequence of regions (A, B,C) with the same arrangement of micro-modifications (5, 51, 52, 53, 54,55, 56) in an optical waveguide (1) in a further embodiment of theinvention. While the first region (A) is present once, this is followedby two regions with a second arrangement (B) and three regions with athird arrangement (C). In this processed optical waveguide (1) not allregions with micro-modifications (5, 51, 52, 53, 54, 55, 56) arrangedaccording to a specific pattern are present a number of times.

Partial figure c) of FIG. 9 shows a different possible sequence ofregions (A, B, C) with the same arrangement of micro-modifications (5,51, 52, 53, 54, 55, 56) in a further refinement of the invention. Whilethe first region (A) follows each region (A, B, C) not equal to thefirst region (A), the second and third regions (B, C) follow the firstregion (A) in alternation.

Further embodiments of the invention can be represented by arbitrarymathematical series and sequences. Here, in a further refinement of theinvention, an optical waveguide (1) according to the invention comprisesmore than three regions (A, B, C) with different arrangements ofmicro-modifications (5, 51, 52, 53, 54, 55, 56). In a preferredembodiment of the invention, the optical waveguide (1) comprises morethan five regions (A, B, C), in a particularly preferred embodimentcomprises more than ten regions (A, B, C) with differently arrangedmicro-modifications (5, 51, 52, 53, 54, 55, 56).

In partial figures a) and b), FIG. 10 shows the schematic setup of anoptical waveguide (1) with micro-modifications (5, 51, 52, 53, 54, 55,56) induced by focused laser radiation (22). Partial figure a) shows asequence with a multiplicity of regions (A, B, C, D, E, F, G, H, I, J)with different arrangements of micro-modifications (5, 51, 52, 53, 54,55, 56). This sequence of regions (A, B, C, D, E, F, G, H, I, J) withdifferent arrangements of micro-modifications (5, 51, 52, 53, 54, 55,56) is repeated n times (partial figure b)). Here, n, m are naturalnumbers. The number of repetitions of the one sequence with amultiplicity of regions (A, B, C, D, E, F, G, H, I, J) with differentarrangements of micro-modifications (5, 51, 52, 53, 54, 55, 56) isdenoted by m.

In a preferred embodiment of the invention, the number of repetitions ofa sequence with a multiplicity of regions (A, B, C, D, E, F, G, H, I, J)with different arrangements of micro-modifications (5, 51, 52, 53, 54,55, 56) is greater than five and greater than twenty in a particularlypreferred embodiment.

In a further embodiment of the invention, the arrangement of therepetitions of the sequence with a multiplicity of regions (A, B, C, D,E, F, G, H, I, J) with different arrangements of micro-modifications (5,51, 52, 53, 54, 55, 56) alternates in terms of the alignment of thearrangement thereof.

In a further embodiment of the invention, the arrangement of therepetitions of the sequence with a multiplicity of regions (A, B, C, D,E, F, G, H, I, J) with different arrangements of micro-modifications (5,51, 52, 53, 54, 55, 56) is a mixed form of alternating and accordantalignments of the arrangement thereof.

LIST OF REFERENCE SIGNS

-   1 Optical waveguide-   11 Core of the optical waveguide-   12 Cladding of the optical waveguide-   13 Coating, buffer and/or further coatings of the optical waveguide-   14 End cap-   15 Proximal end of the optical waveguide-   16 Distal end of the optical waveguide-   17 Optical waveguide axis-   2 Laser beam-   20 Device for introducing micro-modifications into an optical    waveguide-   21 Symbolized focusing optical unit-   22 Focused laser beam-   23 Deflection mirror-   24 Focusing optical unit-   25 Optical axis-   31 Rotation device-   32 Holder/guide for the optical waveguide-   33 Lateral positioning device-   34 Vertical positioning device-   α Rotation of the optical waveguide about the optical waveguide axis-   β₁, β₂, β₃ Rotation of the incoming beam direction of the laser beam-   40 Method for introducing micro-modifications into optical    waveguides-   41 Fixing the optical waveguide in a holder-   42 Focusing laser radiation in a focal position-   43 Moving the focal position through the optical waveguide according    to a predetermined pattern-   44 Repetition of one of the movements of the focal position through    the optical waveguide according to a predetermined pattern-   5, 51, Micro-modification-   52, 53, 54,-   55, 56-   γ Angle of the longitudinal alignment of the micro-modifications in    relation to the optical waveguide axis-   A, B, C, Radial sectional planes through the optical-   D, E waveguide; these can also be inclined-   F Axial sectional plane through the optical waveguide-   A, B, C, Regions of the optical waveguide with micro-modifications-   D, E, F, are arranged therein-   G, H, I, J-   m Number of the repetitions of a sequence with a multiplicity of    regions with different arrangements of micro-modifications-   n Maximum number of repetitions of a sequence with a multiplicity of    regions with different arrangements of micro-modifications

The invention claimed is:
 1. An optical waveguide, comprising an opticalwave-guiding core, and a region in the optical waveguide, whereinmicro-modifications are arranged in the region of the optical waveguide,arrangement of the micro-modifications is ordered, themicro-modifications are arranged on at least two sectional planes, theat least two sectional planes are located along an optical waveguideaxis, the at least two sectional planes lie substantially perpendicularto the optical waveguide axis, the arrangement of themicro-modifications on the at least two sectional planes is obtained byone or more parameters from a group of parameters comprising thesymmetric arrangement of the micro-modifications, the density of themicro-modifications on the at least two sectional planes, the size ofthe micro-modifications, the distance of the micro-modifications fromthe optical waveguide axis, the distance between themicro-modifications, the alignment of the micro-modifications or otherparameters, with the aid of which the position and distribution of themicro-modifications or the size or outer form thereof, and themicro-modifications are arranged as at least one hollow cone formed overthe at least two sectional planes, with the longitudinal axis of the atleast one hollow cone lying on the optical waveguide axis.
 2. Theoptical waveguide according to claim 1, wherein the arrangement of themicro-modifications on a first sectional plane of the at least twosectional planes is repeated on at least one second sectional plane ofthe at least two sectional planes.
 3. The optical waveguide according toclaim 2, wherein the at least one second sectional plane on which thearrangement of the micro-modifications on the first sectional plane isrepeated is rotated by an angle in relation to the first sectionalplane.
 4. The optical waveguide according to claim 2, wherein thedistance between the first sectional plane and the at least one secondsectional plane on which the arrangement of the micro-modifications isrepeated is greater than the extent of a micro-modification.
 5. Theoptical waveguide according to claim 2, wherein the at least one secondsectional plane with micro-modifications, which has a differentarrangement with respect to the first sectional plane, lies between thefirst sectional plane and the at least one second sectional plane onwhich the arrangement of the micro-modifications of the first sectionalplane is repeated.
 6. The optical waveguide according to claim 1,wherein the micro-modifications on the at least two sectional planes arearranged in a rotationally symmetric manner about the optical waveguideaxis.
 7. The optical waveguide according to claim 1, wherein the atleast one hollow cone comprises a plurality of hollow cones, with thehollow cones having different diameters and the longitudinal axes of thehollow cones lying on the optical waveguide axis.
 8. The opticalwaveguide according to claim 1, wherein the region in the opticalwaveguide in which micro-modifications are arranged is subdivided intoat least two portions in the direction of the optical waveguide axis, inwhich portions different alignments and embodiments of orderedmicro-modifications are introduced.